This invention relates to powder-actuated fastener drive tools, and more particularly to a hammer-activated, powder-actuated drive tool for driving a fastener by means of an explosion of a cartridge or "power load".
More particularly, the present invention is directed to improvements in a tool of the foregoing type and more particularly, a low velocity type of tool. A low velocity type tool includes a piston which is driven by the explosive force of the power load, and drives the fastener into a workpiece. A so-called high velocity tool does not include such a piston, but rather the fastener is driven directly by the explosive force of the power load.
One such low velocity tool is shown and described in U.S. Pat. No. 4,025,029 dated May 24, 1977, to John A. Kotas and Eugene J Haupt. That tool has been further improved by the addition of an external safety spring member which biases the relatively telescoping parts thereof apart somewhat. This biasing is such as to preclude contact of the power load by the activating pin or bolt mechanism until the tool is physically pressed against a workpiece surface so as to telescopically collapse the parts thereof and overcome the safety spring biasing force.
At least one tool is also known, for example as shown in U.S. Pat. No. 4,252,259, Brosius, issued Feb. 24, 1981, which utilizes an internally mounted safety spring to achieve the same end. However, in both of these arrangements, the norma biasing force of the safety spring also leaves an open interior space within the tool directly behind the power load receiving chamber. The power load may readily fall by gravity into this open space in the event the forward end of the tool is rotated above a horizontal position relative to the rear end thereof. This renders the tool unusable, whereupon the tool must be reopened to reinsert the power load in the chamber. This makes installation of fasteners in overhead panels or workpieces, or indeed in any workpiece which would require tilting of the tool front end beyond a horizontal plane, impossible. Advantageously, the present invention provides additional novel power load retaining means for preventing such dislodgement of the power load prior to activation thereof, while maintaining the desired action of the safety spring.
As an additional matter, the prior art tools have generally included a handgrip portion separately formed, usually by molding, from a suitable plastics material. This handgrip portion is then press fitted or otherwise non-removably engaged with one or more structural housing or other parts. These include structural members for mounting the activating pin or bolt and one or more biasing springs, including the above-mentioned internal safety spring, and an elongate tubular piston guide in which a fastener-engaging piston is slidably mounted. Such additional structural members have generally also included a retaining bushing for slidably mounting the activating pin or bolt as well as abutting one end of a biasing spring for normally biasing the bolt away from the fully advanced or power load-activating position thereof. A second bushing or retaining member is often provided for retaining the above-mentioned safety spring in the desired position in the housing. An additional, external tubular housing member is also provided.
This latter housing member has also often been provided with an enlarged end portion having through apertures for receiving a piston guide-retaining and piston-resetting pin member inserted therethrough. This pin member generally defines the forwardmost, or fully telescopically extended positions of the piston guide and fastener-engaging piston respectively relative to the housing. An additional friction member is also often included for providing some slight frictional engagement between the tubular housing and the piston guide. Heretofore, all of the foregoing parts have been separately provided, generally being formed of metal materials by suitable forging and/or machining procedures, and then assembled.
However, we have found that many of the foregoing parts are essentially non-loadbearing parts with respect to the load and forces experienced upon activation of the power load. Accordingly, the present invention advantageously provides a one-piece integrally molded hand grip and housing member of a suitable plastics material. This one-piece member is so formed and configured as to perform the functions of many of the foregoing, previously separately provided parts, thus realizing a great savings in expense of the manufacture and assembly of the tool of the invention.